Sending SMS from the site to a mobile phone, in which direction to dig?

Question

mobile connection

Please share resources or explain in general terms how you can implement sending SMS messages to your phone from a site, for example, like in Google, is a verification code sent if there is a double authentication?
I want to develop further and learn more and more, but I haven’t come across this yet and I don’t know what it’s called at all, do I need any engines for this or something else, I don’t know where to dig at all.

Answer 1

One of the first links on request "sms api"
smsc.ru/api/